AGL Energy shareholders have vented their frustration at the black hole of information emanating from the embattled company on its drawn-out strategic review, as concern mounts about the credibility of the review process when the chairman and chief executive are soon to be replaced.

The strategic review is complicated by a chaotic power and gas market that has battered earnings for AGL and Origin Energy, and means the expected recovery in the companies’ earnings will be much more subdued than investors had hoped.